San Andres Squeeze film dampers (SFDs) are virtually the only means to provide structural isolation and vibration energy dissipation in aircraft engines and light hydrocarbon centrifugal compressors. These high performance rotor-bearing systems operate above the natural frequencies of the flexural modes. When the system passes through critical speeds large dynamic loads are induces. This may cause very high amplitude vibrations at the rotor and bearing supports. Under these operating conditions, oil lubricated SFDs as well as dynamically loaded journal bearings are prone to develop regions where the lubricant is foamy, which greatly reduces their dynamic force capacity. This pervasive phenomenon is well known in industry but still lacks proper physical understanding and sound analytical modeling.
In this study measurements of dynamic pressure fields and rotor motions will be performed on a modified journal bearing and SFD test rig operating with a foam-like lubricant and under dynamic loads exerted from a shaker system. Fundamental understanding of bubbly flow fields will be gained through high-speed photography studies and image identification techniques which will be used to track the time evolution and spatial structure of the air bubbles within the thin film flow. In addition, imbalance response measurements in an industrial size rotor supported on SFDs, constructed with prior NSF support, will be conducted to identify damping force coefficients within an operating region where air entrapment occurs naturally. The research products will be valuable to the design of SFDs in critical turbomachinery applications, of process fluid film bearings and of seals in multiple-phase pump applications. ***
